Researchers study miscanthus, switchgrass pests

By Anna Austin

Miscanthus and switchgrass, two of the leading cellulosic ethanol feedstock contenders, just like any other crops, are threatened by pests that need to be studied and carefully mitigated. Researchers at the University of Illinois Energy Biosciences Institute have recently identified potential pathogenic nematodes-microscopic, wormlike organisms-of both crops and at what levels they are present in different areas.

In a 2008-'09 nematode survey, the group analyzed samples from 37 miscanthus and 48 switchgrass plots in Illinois, Georgia, Iowa, Kentucky, South Dakota and Tennessee. They found that all sample sites had at least two nematode species that have been reported to reduce biomass in most monocotyledon hosts.

The presence of nematodes is not unheard of, however, as the organisms provide a variety of functions to soil systems including nutrient mineralization through feeding interactions.

Lead UI researcher Tesfamariam Mekete told Biomass Magazine that results obtained thus far did not come as a surprise. "The result of our first survey fits in our preliminary hypothesis and expectations," he said. "Most of the nematodes we identified are common parasites of monocotyledon plants such as corn."

The levels of the nematodes found in the switchgrass and miscanthus samples were comparable to densities found in other crops, Mekete said, but the damaging population thresholds for the biofuel crops are still unknown. Damage symptoms observed by the researchers included visible stunting of lateral roots and destruction of the fibrous root system, which could contribute to a decline in biomass yield.

Currently, there are several control methods for a given nematode in different crops, Mekete said, but there is no information available on bioenergy crops such as switchgrass and miscanthus. "Though we are screening some biocontrol agents and other available methods," he said.

The next step for the research team will be work on host suitability and damage threshold densities in a greenhouse setting. Mekete said the group plans to set up field experiments at Urbana and Havanna, Ill., in the summer.
Eventually, they hope to develop species-specific DNA tests to help identify nematodes in order to develop control tactics.

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